Charges for waiting are charged per minute. The charge calculated from the time the Captain has arrived at the requested pickup location until the customer is in the car, is called initial waiting. Once the ride is in progress, and if the car is traveling slower than 16KM/H (which happens during traffic) then in-journey waiting is charged. The first 3 minutes of wait time are not charged.
You can check the waiting charges by going to App Menu > Settings > Rates.